The invention relates to a device for detecting labels on a carrier material.
A device of this type is known from reference DE 199 21 217 A1, wherein this device for detecting labels on a carrier material is provided with a transmitter for emitting ultrasonic waves and a receiver for receiving ultrasonic waves. For the detection, the carrier material provided with the labels is guided through the space between transmitter and receiver. The ultrasonic waves are weakened differently, depending on whether only the carrier material itself or the carrier material with a label attached thereto is detected by the ultrasonic waves in the area between transmitter and receiver. The respective differences in the receiving signal at the receiver output are detected by comparing the received signal to a threshold value, wherein this threshold value is adapted with the aid of a balancing operation to the receiving levels that occur. During the balancing operation, which is realized before the label detection, the threshold value level for the carrier material arranged between transmitter and receiver and/or a label attached thereto is determined automatically in dependence of the recorded receiving signal.
With this type of device it has proven to be a disadvantage that a secure detection of labels is not guaranteed, in particular for more bulky carrier materials such as those composed of paper.